Radio frequency telecommunication systems commonly employ directional couplers, hybrids, power splitters and combiners as building blocks for various tasks such as signal routing, combining and monitoring. In addition, these systems may employ power amplifiers that use multiphase couplers to satisfy key performance metrics over a large frequency bandwidth.
Generally, multiphase couplers are implemented using an arrangement of distributed transmission lines in close proximity. To reduce circuit area, however, it is desirable to use lumped element components wherever possible using monolithic microwave integrated circuits (MMIC).
Lumped element MMIC couplers can be designed to operate over a large frequency bandwidth as shown in U.S. Pat. No. 5,045,821. However, performance is significantly reduced when interfacing such couplers to large active semiconductor devices with wide distributed bus bars.